‘DOUBLE EXTRACTION TECHNIQUE’ FOR REMOVAL OF WELL FIXED COMPONENTS IN REVISION TOTAL KNEE ARTHROPLASTY–SOUTHAMPTON EXPERIENCE

Abstract

Removal of solidly fixed implants is a challenge in revision knee arthroplasty. It is fraught with the risk of intraoperative fractures and bone stock vital for the success of subsequent revision surgery. We describe the double extraction technique for extraction of solidly fixed implants. This technique was first tested in laboratory setting and then replicated in the operation theatre with successful results.

In this retrospective study we analysed all our patients in which we used the double extraction technique for the removal of solidly fixed implants. In this procedure, the surgeon and the assistant each place an osteotome on the cement metal interface at symmetric positions, directly opposite each other on the medial and lateral sides. They deliver synchronous blows with a mallet at positions around the interface until the cement fractures. The femoral component can then be easily removed. The technique was tested in a laboratory before it was used clinically. Polyurethane mouldings, representing a suitable substrate for cementing metal components were fixed on to a steel rod of similar weight and length as the lower leg. Stainless steel discs (40mm diameter x 4mm thickness) were cemented on to the polyurethane substrate to form a model of a cemented implant. The discs were instrumented to allow recording of the mechanical processes caused by the double extraction technique and to allow comparison with the single osteotome extraction technique. The methodology successfully demonstrated that the double osteotome technique increases the contact force of the second blow. When the synchronous blows are delivered, less energy is expended in the movement of tibia and more is contributed to the removal of the component.

In this study we looked at a total of 206 patients were the solidly fixed tibial and femoral components were removed using the double extraction technique. There were 86 men and 126 women. The mean age of the patients was 66.8 years (range 37–87 years). Only patients with solidly fixed implants were included in this study. Stability of implants was assessed with preoperative radiographs and then confirmed intraoperatively. Patients with loose implants intraoperatively were excluded from this study. We present our results with use of this technique in 206 patients with follow up of 1 to 5 years.